Mobile ad hoc network consists of wireless nodes, and is insfrastructureless network. Because of the limited radio transmission range, a packet from source to the destination may need multiple hops. Every node in the network can be a router. Because nodes are free to move randomly,  the link in the route may be broken.
	The existing routing protocols mostly continue use a route until a link breaks. Then the source will rebuild a new route. It causes some problems: first it will take time to determine the link is broken, second, when node builds a new route, the packet will be dropped.